Extensions of Mendelian Inheritance

What are the chances that a man with type O blood and a woman with type AB blood could have a child with type O blood?

0%

Coloration of the feathers of parakeets is controlled by two genes. The dominant allele Y for one gene leads to yellow coloration. The corresponding recessive allele y results in white feathers. The dominant allele A for a separate gene leads to blue coloration. The corresponding allele a results in white feathers. Birds that inherit at least one copy of the dominant alleles for both genes have green feathers while birds that are homozygous recessive for both genes have white feathers. Suppose two birds known to be heterozygous for both the yellow and blue coloration genes are mated. What fraction of the offspring would be expected to have white feathers?

1/16

In chickens, feather color can be black or splash (white with black spots). If a black rooster is crossed to a splash hen, the offspring show an intermediate blue color. If a splash rooster is crossed to a blue hen, what fraction of the offspring will be expected to have blue feathers?

1/2

For dog coat color, the dominant S+S+allele results in full pigmentation while the recessive sIsIallele leads to white patches on the legs and belly called Irish spotting. Two fully pigmented dogs have puppies with Irish spotting. What is the approximate fraction of offspring with Irish spotting expected from this cross?

1/4

In chickens, feather color can be black or splash (white with black spots). If a black rooster is crossed to a splash hen, the offspring show an intermediate blue color. If a blue rooster is crossed to a blue hen, what fraction of the offspring will be expected to have black feathers?

1/4

For summer squash, the dominant allele Y for gene 1 leads to yellow color while the recessive allele y leads to green color. Alleles of gene 2 can prevent color formation, with the dominant allele W leading to white squash while the recessive allele w does not interfere with color development. For the cross YyWw x YyWw, what is the fraction of offspring that will be white?

12/16

Suppose a man with type A blood and a woman with type B blood have a child with type O blood. What are the chances that they could have a child with type AB blood at a later time?

25%

Coloration of the feathers of parakeets is controlled by two genes. The dominant allele Y for one gene leads to yellow coloration. The corresponding recessive allele y results in white feathers. The dominant allele A for a separate gene leads to blue coloration. The corresponding allele a results in white feathers. Birds that inherit at least one copy of the dominant alleles for both genes have green feathers while birds that are homozygous recessive for both genes have white feathers. Suppose two birds known to be heterozygous for both the yellow and blue coloration genes are mated. What fraction of the offspring would be expected to have blue feather coloration?

3/16

Among the children of two parents with the HbA HbS genotype, what percentage is expected to be unaffected by sickle cell anemia and resistant to malaria?

50%

For harebell plants, dominant alleles for two separate genes are needed to produce blue petal color. Suppose gene 1 has alleles P and p and gene 2 has alleles B and b. Only plants with at least one P allele and at least one B allele will have blue petals; all other genotypes lead to white petals. For the cross PpBb x PpBb, what fraction of the offspring are expected to have white petals?

7/16

Suppose that the covering on corn kernels can have a purple color due to the dominant allele P of gene 1. The genotype pp leads to a colorless covering. Alleles of gene 2 can mask the purple color, with the dominant allele C having no effect but genotype cc changing the purple color to colorless. Alleles of gene 2 have no effect on plants with genotype pp for gene 1. For the cross PpCc x PpCc, what fraction of the plants are expected to have colorless covering on their corn kernels?

7/16

In fruit flies, dominant alleles for two different genes are required for red eye color. Suppose gene 1 has alleles R and r and gene 2 has alleles E and e. Only flies with at least one R allele and at least one E allele will have red eyes; all other genotypes lead to white eyes. For the cross RrEe x RrEe, what fraction of the offspring are expected to have red eyes?

9/16

Which of the following demonstrate gene redundancy?

A gene duplication event where a paralog can carry out the function of a missing gene. An increase in function of one protein to compensate for the loss of function of a similar one.

Lethal alleles

Alleles that have the potential to cause death

Suppose a mother with the IAi genotype and a father with the IBi genotype have one child with type A blood and one child with type AB blood. Which is the best description of the observed genetic patterns?

Codominance is observed for the child with type AB blood while complete dominance is observed for the child with type A blood

Suppose a mother with the IAi genotype and a father with the IBi genotype have two children, one with a codominant genotype and one with a genotype demonstrating complete dominance. The children's genotypes can be _____

Codominant = IAIB; Complete dominance = IBi

Which of the surface antigens related to blood type would be found on the red blood cells of an individual with the IAIB genotype?

Each red blood cell would carry both surface antigen A and surface antigen B

Incomplete penetrance

Failure to express a dominant phenotype even though the individual carries the dominant allele for that trait.

Simple Mendelian inheritance

Follows a strict dominant/recessive relationship

Two genes controlling the synthesis of different pigments are responsible for feather coloration in Australian parakeets. The dominant allele Y for one gene leads to production of psittacofulvin for yellow coloration. The corresponding recessive allele y prevents yellow pigment production. The dominant allele A for a separate gene leads to eumelanin pigment, appearing blue in reflected light. The corresponding allele a prevents blue pigment production. A bird with the Yyaa genotype will have yellow feathers, one with the yyAa genotype will have blue feathers, while one with the YyAa genotype will have green feathers. What is the interaction between these two genes?

Gene A modifies the expression of gene Y

Codominance

Heterozygote expresses both alleles simultaneously

Incomplete dominance

Heterozygote has intermediate phenotype.

For which of the following genotypes would the effects of codominance be observed in the individual's phenotype?

IAIB

What is the name for the situation where heterozygotes have greater reproductive success than either of the two homozygotes?

Overdominance

Codominance

Pattern in which both alleles are expressed in the heterozygote without blending

Incomplete dominance

Pattern producing an intermediate phenotype in the heterozygote

For dog coat color, the dominant S+S+allele results in full pigmentation while the recessive s^I s^I allele leads to white patches on the legs and belly called Irish spotting. Suppose that a cross between a fully pigmented female and an Irish-spotted male yields some puppies with the mother's phenotype and others with the father's phenotype. What is the genotype of the fully pigmented female parent in this cross?

S+s^I

Why does an organism that inherited one or more temperature-sensitive lethal alleles survive at low temperatures?

The protein product of the temperature-sensitive allele can function at low temperatures

Sex-influenced

Trait is inherited by both sexes but with different dominant/recessive patterns

Sex-limited

Trait occurs in only one of the two sexes

X-linked

Traits for which males inherit only one allele while females inherit two alleles

Himalayan coloring in rabbits is due to a dominant allele that codes for a tyrosinase enzyme which participates in the production of the dark pigment melanin. In cold temperatures, dark coloring is only found in the ears, nose, and feet of the animal. White coloration develops on body areas where blood flow keeps the animal warm. Which most accurately describes this phenomenon?

Tyrosinase is a temperature-sensitive enzyme

The transmission pattern of sex-linked genes depends on whether the gene is on the_____or ______chromosome and on the sex of the offspring

X;Y

A cell with at least one copy of a wild-type allele will typically produce ______ of the protein specified by this allele

a functional version

Huntington disease is a lethal condition for which symptoms begin to appear in middle age. The age at which a person begins to show disease symptoms is called the

age of onset

The following pathway is proposed to explain the inheritance of purple flower color in pea plants: Colorless Precursor→Colorless Intermediate→Purple Pigment. A dominant allele for gene C provides an enzyme that converts Colorless Precursor→Colorless Intermediate. A dominant allele for gene P provides an enzyme that converts Colorless Intermediate→Purple Pigment. An explanation of why plants with CCpp and ccPP genotypes have white petals while plants with the CcPp genotype have purple flowers is ___

complementation occurs in the purple-petaled plant, showing that the mutations preventing color in the white plants are in different genes

A temperature-sensitive allele that causes the death of an organism only with exposure to a specific range of temperatures is a(n) ______ lethal allele.

conditional

G6PD deficiency results from a deficiency of an enzyme that is especially important for protecting red blood cells from harmful oxidizing agents. People with G6PD deficiency can live healthy lives but can die from severe destruction of red blood cells after eating fava beans. Fava beans have multiple oxidizing agents that can endanger the red blood cells in these patients. The allele for G6PD deficiency would be described as a _____lethal allele

conditional

Parents can unknowingly pass on a dominant lethal allele for Huntington disease to their offspring because the _____

disease symptoms often do not appear until after the parent has had children

The type of mutation in which a protein produced by a mutant allele acts against a normal protein is called a_____mutation

dominant negative

Brittle bone disease is caused by a mutation in a gene that codes for collagen fibers. The product of the mutant allele binds to normal collagen and disrupts proper fiber formation. The mutation can be described as a ______ mutation

dominant-negative

The ability to prevent the symptoms of phenylketonuria by restricting the diets of patients who inherit the disease is an example of _______ effects on a phenotype.

environmental

The effect of phenylketonuria, an autosomal recessive disorder in which individuals are unable to metabolize phenylalanine, can be altered by a restricted diet with limited amounts of phenylalanine. This is an example of ______

environmental effects on gene expression

For summer squash, the dominant allele for one gene leads to yellow color while the recessive allele for this gene leads to green color. When the genotype of a second gene is either homozygous dominant or heterozygous, neither color is produced and the squash is white. The effect of the second gene on the first one is called ____

epistasis

When Blue-Eyed Mary plants inherit at least one dominant allele for a gene for flower color, their petals are blue to match their name. If plants are homozygous recessive for a second gene, however, they develop white petals. The effect of the second gene on the first flower color gene is called

epistasis

A gene that codes for a product that is necessary for the survival of an organism is called a(n) ______ gene

essential

Which of the following can explain why pleiotropy occurs?

expression of one gene that affects cell function in more than one way expression of one gene at different stages of development expression of one gene in different cell types

Which choice does not represent an explanation for pleiotropy?

expression of two genes that affect cell function in more than one way

A patient with sickle cell disease may experience a painful episode leading to tissue and organ damage because cells carrying hemoglobin S _____

form abnormal crescent shapes that block capillaries, depriving nearby cells of oxygen

For Australian parakeets, the dominant allele of one gene causes yellow-colored feathers. The dominant allele of another gene causes blue pigment to be made, resulting in green-colored feathers. This is an example of ____

gene interaction

The pattern where allelic variants of two different genes affect a single trait is called

gene interaction

Two genes controlling the synthesis of different pigments are responsible for feather coloration in Australian parakeets. The dominant allele Y for one gene leads to production of psittacofulvin for yellow coloration. The corresponding recessive allele y prevents yellow pigment production. The dominant allele A for a separate gene leads to eumelanin pigment, appearing blue in reflected light. The corresponding allele a prevents blue pigment production. A bird with the Yyaa genotype will have yellow feathers, one with the yyAa genotype will have blue feathers, while one with the YyAa genotype will have green feathers. The effect of gene A on gene Y is called

gene modification

Suppose loss-of-function mutations in two separate genes do not produce any phenotypic effects but combining the two loss-of-function mutations in one organism shows a difference in phenotype. What is the most likely explanation?

gene redundancy

When one gene can compensate for the loss of function of another gene, the phenomenon is called

gene redundancy

When more than one wild-type allele occurs in a population, the phenomenon is called

genetic polymorphism

The difference between type A and type B blood is produced by ______

glycosyl transferase enzymes with different activities

Familial hypercholesterolemia is due to a lack of receptors for low-density-lipoproteins on the surfaces of cells. Both homozygous dominant individuals and heterozygous individuals suffer from the disease. Even with a dominant allele for the receptor, heterozygotes do not produce the receptor proteins in sufficient amounts. This pattern of expression is described as ______.

haploinsufficiency

If a heterozygous individual shows a disease phenotype despite having one functional allele, the inheritance pattern is called

haploinsufficiency

Individuals with an HbS HbS genotype suffer from sickle cell anemia because they produce ______, a variant that causes their red blood cells to form ______

hemoglobin S; crescent shapes when oxygen concentration is low

For the white spotting phenotype in dogs, the regions with fewer melanocytes and lighter coloration are located ____

in areas farthest away from the spinal cord

The enzyme glycosyl transferase is the product of the gene for ABO blood type. In determining the phenotype of individuals inheriting specific alleles of this gene, the product of the i allele is ______ and the products of the IA and IB alleles are _____

inactive; active

Suppose a genetic test shows that a woman has inherited the dominant BRCA1 allele that causes breast cancer. If she does not develop breast cancer in her lifetime, the phenomenon is called____

incomplete penetrance

The pattern observed when a heterozygote does not show the trait associated with the dominant allele is

incomplete penetrance

What are the two fundamental laws of inheritance discovered by Mendel?

law of independent assortment law of segregation

Even though it leads to sickle cell disease in homozygous individuals, the allele HbS is retained in some populations because it confers resistance to _____ for heterozygotes.

malaria

Dark pigmentation of fur in dogs depends on the production of ______ by cells called ______

melanin; melanocytes

A dog's fur will have white patches if cells called _______do not produce the pigment melanin.

melanocytes

White spots occur in the coats of dogs as a result of a decrease in the number of _____ that are responsible for producing dark pigment.

melanocytes

A single gene for white coloring on the coats of dogs has four alleles with a hierarchy of dominance. Various combinations of these alleles can lead to solid coat, Irish-spotting, piebald-spotting, and white coats. This inheritance pattern for white coloring is due to the existence of ______ for the gene for coat coloring.

multiple alleles

Which phenomenon is observed in a population when three or more alleles can be found for a single gene?

multiple alleles

Rarely-occurring alleles that have genetic changes making them defective in protein production are called ______ alleles

mutant

When a preexisting allele is changed to a new version that no longer codes for a functional protein, the new allele is called a_____allele

mutant

A gene that produces a beneficial product that is not absolutely required for survival of the organism is called a(n) ______ gene.

nonessential

In corn plants, the enzyme alcohol dehydrogenase functions as a homodimer, where the two subunits can be identical or slightly different. One type of subunit is stable but somewhat inactive, while another type of subunit is active but somewhat unstable. Homodimers composed of one of each subunit are both stable and active. Heterozygous plants that can produce both types of subunits have an advantage due to ______

overdominance

Suppose protein C functions as a homodimer, where the two subunits can be identical (C1C1 or C2C2) or slightly different (C1C2). Further suppose that the C1C2 homodimer is more stable than either homodimer with identical subunits. Heterozygous individuals would then have an advantage due to

overdominance

The situation where a heterozygote has a characteristic that makes it more likely than either homozygous individual to reproduce in a given environment is called

overdominance

While causing sickle-cell anemia in homozygous individuals, the product of the HbS allele provides resistance to malaria in individuals with the HbA HbS genotype. This advantage to heterozygotes demonstrates _____

overdominance

One gene can compensate for the loss of function of another gene in cases where a duplicate gene called a(n) _____has arisen over evolutionary time or when the function of another ______ can be increased to compensate for the missing protein product of the non-functional gene.

paralog; protein

Genes that may differ slightly in sequence but were derived by duplication during evolution are called

paralogs

Human hemoglobin is a complex of four protein chains produced by two different genes, one for alpha-hemoglobin and one for beta-hemoglobin. These genes have sequence differences but similarities suggest that they were produced by gene duplication earlier in evolutionary time. These genes would be described as _____

paralogs

The allele for sickle cell anemia leads to multiple changes in the individual's phenotype, including the type of hemoglobin produced, the shape of red blood cells, the onset of anemia, and reduced susceptibility to malaria. The name for these multiple effects on phenotype is ______

pleiotropy

A population that contains more than one wild-type allele demonstrates genetic ____

polymorphism

A lethal allele usually shows a(n) ______ inheritance pattern

recessive

For sweet pea plants, two genes are involved in purple coloration of flower petals. At least one copy of each of the dominant alleles C and P are required for purple color while the genotypes cc or pp result in white colored petals. For example, a pea plant with the genotype Ccpp, although inheriting one of the dominant alleles, will have white flowers. In this case, the effect of the P gene on the expression of the C gene is ______.

recessive epistasis

Suppose that the covering on corn kernels can have a purple color due to the dominant allele P of gene 1. Alleles of gene 2 can mask this color, with the dominant allele C having no effect but genotype cc changing the purple color to colorless. For corn with the genotype Ppcc, what is the effect of gene 2 on gene 1?

recessive epistasis

Suppose that there are two male mice who are homozygous for the same allele. They are raised under the same environmental conditions: receiving the same types of foods in cages exposed to the same ranges of temperature. Despite this attention to animal care, one mouse dies and the other survives. Which type of allele is likely to be responsible for this death?

semilethal allele

The development of specific sex organs, such as the presence of testes in human males and ovaries in human females is due to _______inheritance.

sex limited

A trait that is expressed in only one sex and not seen in the opposite sex shows ______ inheritance

sex-limited

For humans, the presence of ovaries in females and testes in males is an example of ______ inheritance.

sex-limited

A phenomenon involving animals of the same species, but of opposite sexes, that have different physical features is called_____

sexual dimorphism

Male birds often have more ornate and colorful feathering patterns than female birds. This is an example of ____

sexual dimorphism

In fruit flies, the para mutation causes a change in a sodium channel necessary for conducting nerve signals. Mutant flies have normal movement at 22oC but become immediately paralyzed at 29oC. The paralysis is reversed when the temperature returns to 22oC. The para mutation is most likely due to a(n) ______.

temperature-sensitive allele

The following pathway is proposed to explain the inheritance of purple flower color in pea plants: Colorless Precursor→Colorless Intermediate→Purple Pigment. A dominant allele for gene C provides an enzyme that converts Colorless Precursor→Colorless Intermediate. A dominant allele for gene P provides an enzyme that converts Colorless Intermediate→Purple Pigment. An explanation for why plants with the ccPp genotype have white petals while plants with the CcPp genotype have purple petals is that _____

the cc genotype exerts epistasis over the Pp genotype, preventing purple color formation

Individuals with the HbA HbS genotype do not develop malaria because ______

the presence of hemoglobin S prevents the malarial parasite from reproducing within their bodies

Which two of the following affect the transmission pattern of sex-linked genes?

whether the gene is on the X or Y chromosome the sex of the offspring

The most commonly occurring allele in a population is called the____-____allele

wild-type

In the general population, 1/150 people are carriers for the allele for Tay-Sachs disease. A child with the disease is born to healthy parents who are unaware of their carrier status. The allele that prevents the disease in the parents is a ______ allele and the one that causes the disease is a ______ allele.

wild-type; mutant